The present invention relates to a new and improved construction of a door drive for doors of elevator cars.
In its more particular aspects the present invention specifically relates to a new and improved construction of a door drive for a horizontally opening elevator car sliding door. This sliding door contains at least one door panel of a predetermined width. The door drive contains at least one driving means comprising endless belt-shaped driving means guided at two deflection rolls or pulleys which are arranged at a supporting structure of the elevator car. The driving means are driven by a motor. At the drive run of the belt-shaped driving means, there is arranged at least one entrainment or coupling bracket which is fixed to one panel of the sliding door. The door drive can be selectively utilized for various door panel widths.
In a motor-driven multicomponent sliding door for an elevator car as known, for example, from German Utility Model No. 7,044,605.8, published May 19, 1971, each trailing door panel moves half as quickly as the related leading door panel. The drive motor is arranged at the slow-moving door panel and drives one of two chains which are guided at deflection sprocket wheels also arranged at the door panel. A door entrainment or coupling bracket of a leading door panel is fastened to the drive run of the aforementioned one chain.
It is a disadvantage of this arrangement that during each door movement the mass of the whole door drive must be moved. The usually small clearance between the elevator car and the elevator hoistway or shaft has to be correspondingly enlarged for free travel of the door drive motor. A further disadvantage exists in that a flexible supply line or conductor is required for powering the drive motor.
A door drive as known, for example, from U.S. Pat. No. 4,149,615, granted Apr. 17, 1979, is arranged on the roof of an elevator car and is suitable for different cars, different types of sliding doors and different door widths. In FIG. 1 of this patent there is shown a telescopic sliding door equipped with a fast-moving door panel and a slow-moving door panel. The slow-moving door panel is driven by means of an endless drive belt which extends over the whole width of the car. At the same door panel there is constructed a drive arrangement for displacing or moving the second door panel at a greater speed. The complete door driving means is arranged on supporting structure which in its extent corresponds to the total width of the elevator car and which can be adjusted in horizontal direction and vertical direction. The complete door driving means is connected with the elevator car via damping or shock-absorbing elements.
It is a disadvantage of this door drive that the driving means extends over practically the entire width of the elevator car and projects on one side by more than one door panel width beyond the closed door in the closed state of the elevator car opening. As a result, follow-up or retro-adjusting work is required for adapting the supporting structure to different elevator car widths, and also transport and mounting problems may arise due to the possible great lengths or extents of the supporting structure. Apart therefrom the door drive does not possess gradual starting acceleration or run-out deceleration due to a deflection of the driving means when opening or closing the sliding door.